package com.hmdp.utils;

import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;
import com.hmdp.entity.Shop;
import lombok.extern.slf4j.Slf4j;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Component;

import java.time.LocalDateTime;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.function.Function;

/**
 * @author luomingliang
 * @date 2022/4/6 22:13
 */
@Slf4j
@Component
public class CacheClient {

    private StringRedisTemplate stringRedisTemplate;

    public CacheClient(StringRedisTemplate redisTemplate) {
        this.stringRedisTemplate = redisTemplate;
    }

    public void set(String key, Object value, Long time, TimeUnit unit) {
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(value), time, unit);
    }

    public void setWithLogicExpire(String key, Object value, Long time, TimeUnit unit) {
        //设置逻辑过期
        RedisData redisData = new RedisData();
        redisData.setData(value);
        redisData.setExpireTime(LocalDateTime.now().plusSeconds(unit.toSeconds(time)));
        //写入redis
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(redisData));
    }

    //缓存穿透
    public <R, ID> R queryWithPassThrough(
            String keyPrefix, ID id, Class<R> type, Function<ID, R> dbFallback,
            Long time, TimeUnit unit) {
        String redisKey = keyPrefix + id;
        //1.从redis中查询商铺缓存
        String json = stringRedisTemplate.opsForValue().get(redisKey);
        //2.判断是否存在
        if (StrUtil.isNotBlank(json)) {
            //3.存在，直接返回
            return JSONUtil.toBean(json, type);
        }
        //判断命中的是否是空值
        if (json != null) {
            return null;
        }
        //4.不存在，根据id查询数据库
        R r = dbFallback.apply(id);
        //5.不存在，返回错误
        if (r == null) {
            //将空值写入redis
            stringRedisTemplate.opsForValue().set(redisKey, "", RedisConstants.CACHE_NULL_TTL, TimeUnit.MINUTES);
            //返回错误信息
            return null;
        }
        //6.存在，写入redis
        this.set(redisKey, r, time, unit);
        //7.返回
        return r;
    }

    private static final ExecutorService CACHE_REBUILD_EXECUTOR = Executors.newFixedThreadPool(10);

    //缓存穿透
    public <R, ID> R queryWithLogicExpire(String keyPrefix, ID id, Class<R> type, Function<ID, R> dbFallback,
                                      Long time, TimeUnit unit) {
        String redisKey = keyPrefix + id;
        //1.从redis中查询实体缓存
        String shopJson = stringRedisTemplate.opsForValue().get(redisKey);
        //2.判断是否存在
        if (StrUtil.isBlank(shopJson)) {
            //3.不存在，直接返回
            return null;
        }
        //4.存在 判断是否过期
        RedisData redisData = JSONUtil.toBean(shopJson, RedisData.class);
        R r = JSONUtil.toBean((JSONObject) redisData.getData(), type);
        LocalDateTime expireTime = redisData.getExpireTime();
        //5.判断是否过期
        if (expireTime.isAfter(LocalDateTime.now())) {
            //5.1 未过期，直接返回商铺信息
            return r;
        }
        //5.2 已过期，需要缓存重建
        //6.缓存重建
        //6.1 获取互斥锁
        String lockKey = RedisConstants.LOCK_SHOP_KEY + id;
        //6.2 判断是否获取锁成功
        boolean isLock = this.tryLock(lockKey);
        if (isLock) {
            //6.3 成功，开启独立线程，实现缓存重建
            CACHE_REBUILD_EXECUTOR.submit(() -> {
                try {
                    //查询数据库
                    R r1 = dbFallback.apply(id);
                    //重建缓存
                    this.setWithLogicExpire(redisKey, r1, time, unit);
                } catch (Exception e) {
                    throw new RuntimeException(e);
                } finally {
                    //释放锁
                    this.unLock(lockKey);
                }
            });
        }
        //6.4 返回过期的实体信息
        return r;
    }

    //获取锁
    private boolean tryLock(String key) {
        Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key, "1", 10L, TimeUnit.SECONDS);
        return BooleanUtil.isTrue(flag);
    }

    //释放锁
    private void unLock(String key) {
        stringRedisTemplate.delete(key);
    }
}
